One technology of the related art allowing mobile nodes to utilize an IP network is called Mobile IPv6 (See for example non-patent document 1). Mobile IPv6 utilizes a router called a home agent (hereafter HA) for communications connected to the mobile node (hereafter MN). When the MN receives a care-of address (address the MN borrows from each network location) via an external network, the MN sends that care-of address along with a binding request containing the MN unique address (hereafter home address) to the HA. When a valid binding request is received, the HA registers the MN information in the internal binding cache.
The node communicating with the MN (hereafter CN), utilizes the home address as the destination address during communication with that MN. The HA receives the packet with the home (destination) address. The HA then relays that packet to the care-of address of the MN. The packet is in this way conveyed from the CN to the MN. The CN supports Mobile IPv6, so when the CN can process the binding request sent from the MN, the CN registers and utilizes the home address and matching care-of address within the binding cache of its own node. The CN can therefore optimize the route to directly communicate with the MN without the HA.
[Patent document 1] JP-A No. 007578/2004
[Non-patent document 11] “Mobility Support in IPv6”, RFC3775 IETF (Internet Engineering Task Force) Request for Comments.